Aug., 1'341
MAGNESIUM AND ZINC ON CROTYL AND METHYLVINYLCARBINYL CHLORIDES 2113
of magnesium turnings and 1.21 equivalent of the appropriate alkyl bromide in six t o eight volumes of absolute ether. One equivalent of 3-chloro-1-ethoxybutyronitrile was diluted with an equal volume of anhydrous ether and added to the alkylmagnesium bromide, After being decomposed with cold, dilute hydrochloric acid and dried over calcium chloride, the ether was removed and the product fractionated under 4-9 mm. pressure. Thc yields reported are based upon the quantity of keto ether ohtained from the first fractionation. The ketones were colorless when freshly distilled, but soon darkencd upon standing in a sealed container. These conlpounds are sparingly soluble in water, but arc miscible in the usual organic solvents. Certain data representing physical properties and analyses for these nine new keto ethers are listed in Table I. Only two of the nine ketones, namely, the n-propyl and n-butyl members, formed semicarbazones, even when the ketones and reagents stood for several weeks.
Semicarbazone of 3-chloro-1-ethoxypropyl n-propyl ketone, m. p. 130' (cor.) with decomposition. Anal. Calcd. for CloH&INaOz: N, 16.83. Found: N, 16.70. Semicarbazone of 3-chloro-1-ethoxypropyl n-butyl ketone, m. p. 104' (cor.) with decomposition. Anal. Calcd. for CIIH~~CINBO?: N, 15.93. Found: N, 15.03
Summary Acrolein was converted into 1,3-dichloropropyl ether, and the latter, in turn, into 3-chloro-lethoxybutyronitrile by interaction with silver cyanide. From the nitrile, by means of the appropriate Grignard reagents, were prepared nine new 3-chloro-1-ethoxypropyl alkyl ketones. AUSTIN,TEXAS
RECEIVEDMAY12, 1941
[CONTRIBUTION FROM
THE
CHEMISTRY DEPARTMENT OF
THE
UNIVERSITY OF CALIFORNIA AT Los ANGELES]
Allylic Rearrangements. XI. The Action of Magnesium and Zinc on Crotyl and Methylvinylcarbinyl Chlorides BY WILLIAM G. YOUNGAND MORTON EISNER Previous communications from this Laboratory have shown that allylic rearrangements occur during the formation and hydrolysis of butenylmagnesium bromides in diethyl ether' and during the reaction of several other metals with the butenyl bromides in boiling SO% In both solvents, diethyl ether and ethanol, the composition of the butene mixtures produced as a result of this rearrangement was independent of the nature of the butenyl (crotyl and methylvinylcarbinyl) bromide mixture, but was related to the molal electrode potential of the metal when the reaction was carried out in boiling 80% ethanol. However, a complete understanding of the rearrangements requires a study of the effect of temperature, solvent, and halide as well as character of the metal. It is the purpose of this paper to present a preliminary report on such a study.
Experimental Part Preparation and Hydrolysis of the Grignard Reagent.A series of experiments on small quantities of butenyl chlorides carried out in the apparatus used in the study3 of butenylmagnesium bromides demonstrated that the coupling reaction, frequently encountered4 with other allylic (1) Young, Winstein and Prater, THISJOURNAL, SI), 289 (1936). (2) (a) Young and Winstein, i b i d . , SI), 441 (1936); (b) Young. Kaufman, Loshokoff and Pressman, i b i d . , 60, 900 (1938). (3) Young, Prater and Winstein, i b i d . , 66, 4908 (1933). (4) (a) Gilman and McGlumphy, Bull. SOC. chim., 48, 1322 (lY28); (b) Gilman and Kirby, THISJOURNAL, 61, 3473 (1929) ; ( c ) Gilman and Zoellner, ibid., 62, 3984 (1930); (d) Gilman and Harris, Rcc. lrazc. c h i m , 60, 10.52 ( 1 9 3 1 ) .
halides, could be minimized by increasing the mole ratios of ether and magnesium turnings t o butenyl chloride provided the chloride was added slowly accompanied by vigorous stirring. When the mole ratios were 30: l 5 : l the yield of Grignard reagent was 86%. The yield was only 409; when the ratios were 7.5:3:1. In order t o conserve both materials and time in working with 0.3-0.7 mole quantities of the butenyl chloride mixtures, we chose a n addition time of three to four hours and mole ratios of 19:lO: 1 for the ether, magnesium and chloride, respectively. The hydrolysis of the Grignard reagent and the recovery and purification of the butenes as dibromobutanes was carried out as described by Young, Winstein and Prater.' The Reaction of Butenyl Chlorides with Zinc.-Mixtures of crotyl and methylvinylcarbinyl chlorides containing different proportions of these primary and secondary butenyl chlorides were converted into butene mixture by the action of zinc in boiling 80% ethanol according t o t h e method used by Young and Winstein.'" However, it was found that the butenyl chlorides were sufficiently volatilc to pass through the purification train along with thc butenes and contaminate the final product. The addition of silver nitrate t o the perchloric acid in the washing train proved an effective means of removing the volatile chloride without causing rearrangement of the butenes. Analysis of the Butene Mixtures.-The composition of butene mixtures formed from the butenyl chlorides was determined either by the dibromobutane reaction rate method of Dillon, Young and Lucas6 in which the necessary or by distillation in a Freycorrections were applied6~*b Hepp column' modeled after the one used by Hurd and Goldsby.s In some cases both procedures were used as a ( 5 ) Dillon, Young and Lucas, THISJOURNAL, 62, lY33 (1930). (6) Young and Winstein, i b i d . , 68, 102 (1936). ( 7 ) Frey and Hepp, I n d . Eng. Chcm., 26, 441 (1933).
( 8 ) Hurd and Goldsby, THISJOURKAL, 66, 1812 (1934)
WILLIAMG. YOUNGAND MORTONEISNER
2114
check on each other. The results of the experiments with magnesium are listed in Table I and those with zinc in 80% ethanol in Table 11. Materials. Magnesium turnings were prepared as needed from bars of the commercial c. P. grade purchased from the Aluminum Corporation of America. The zinc was a mixture of equal parts of dust and 80-mesh which had been activated by the method of Marvel, Sample and Roy.8 Two types of butenyl chloride mixtures were prepared by fractional distillation of a commercial productlo containing equaI quantities of the primary (crotyl) and secondary (methylvinylcarbinyl) chlorides. The two mixtures, contained from 75-95% and 5-25% of primary chloride, respectively, the exact composition being determined before a given butenyl chloride mixture was used.
Discussion of Results Reduction of Butenyl Chloride with Magnesium.-Two different mixtures of crotyl and methylvinylcarbinyl chlorides have been converted into butene 'mixtures by the action of magnesium in ether followed by hydrolysis and by the action of activated zinc in boiling 80% ethanol. The results using magnesium are shown in Table I. The composition of the butene mixtures obtained from both mixtures of butenyl ch1oridese:agrees well with that previously found when butenyl bromides' were used. The discrepancy between runs I and II'resulted from a TABLEI ANALYSISOF BUTENE MIXTURESFROM THE ACTIONOF R~AGNESIUM ON BUTENTLCHLORIDE MIXTURESIN DIETHYL ETHER
.
Run number. . . . . nl'o of butenyl chloride mixture Crotyl chloride, % Methylvinylcarbinyl. chloride, % Reaction rate, K2, of C6HsBm mixture d*sr of dibromide mixture
I
I1
1.4277 82.6
1.4151 24.9
17.4
73.1
0.060R
1.7836
Ana[ytical method Rate 1.2-DiQromobutane (154.7 butene), % dl-2,3-Dibromobutane 21.0 (cis-2-buten4, % meso-2,3-Dib~omobutane (fvuns-Z-butene), To 24.3
0.06O2 1.7810" FreyHepp
Butenes from butenyl bromides
11.6"
54.2
86.4*2.0
45.1
20.4
17.2-3.3
13.4
25.4
2 5 . 5 * l .4
Ratw
A low density due to traces of impurities gives an erroneous analysis. This could be overcome by regeneration of the butenes. Since the sample was small we chose to check the analyqjs by the Frey-Hepp method after regenerating the butenes from the dibromohutane mixture. * Results obtained by Young, Winstein and Praterzbfrom butenyl bromide mixtures. a
(9) Marvel, Sample and Roy, T w s J O W R N A I . , 61, 3241 (193Y) (10) This product was kindly furnished t o us by the Shell Development Company, Emeryville, California, through the courtesy of Dr. E . C . Williams.
Vol. 63
difference in density caused by a trace of impurity in sample 11. This difficulty was over.. come by reconverting sample I1 into a butene mixture which was analyzed in a Frey-Hepp c01umn.~ Reduction of Butenyl Chlorides with Zinc.The results obtained from reduction of different butenyl chloride mixtures by the action of activated zinc in boiling 80% ethanol are listed in Table 11along with those obtained from the action of zinc on butenyl bromides2" They show that the butene mixtures are independent of the composition of the butenyl chloride mixtures used. TABLEI1 FREY-HEPPANALYSIS OF BUTENEMIXTURES PROM THE ACTIONOF ZINC ON BUTENYLCHLORIDE MXXTVRES IN BOILING 80% ETHANOL
. . . . . ,111
Expt. number..
nZiDof butenyl chloride
Crotyl chloride, 70 Methylvinylcarbinyl chloride, % 1-Butene, % cis-2-Butene, 70 trans-%Butene, % '
1,4143 16,O
84.0 69.P 30.8
IV
V
1.4127 1.4299 8.0 93,s 92.0 67.4 32.6
6,s 67.4 32.6
Butenes from butenyl bromide9
..
.. 62 30 7
... ... ...b These results are of qualitative significance only since the gas sample contained some butenyl chloride which made it difficult to recover all of the 2-butene in the FreyThe distillation curves indicate a trace Hepp analysis. of trans-2-butene, probably
